Question

If f(x)= sigma with 5 on top i=2 on bottom (ix+i^2), then f(-2)=?

Answer 1

(4) 26

Explanation:

You want the value of the sum for x = -2:

`\displaystyle f(x)=\sum_(i=2)^5{(ix+i^2)}`

Sum

The sum of integers 2–5 is ...

2 +3 +4 +5 = 14 . . . . . . . coefficient of x

The sum of their squares is ...

4 +9 +16 +25 = 54 . . . . . added constant

So, the sum simplifies to ...

f(x) = 14x +54

Value

The value of the function at x=-2 is ...

f(-2) = 14(-2) +54 = -28 +54 = 26